I have used a NOS "O.S. Mari" plain gut A. The Mari was very low tension and slightly pitch indistinct, though sounded great and would work for a player who is doing mostly slap bass with some basic pizz. I think the "Gotz" gut plain As David Gage are a modern equivalent, and the price is fair.
The Pistoy A is another beast entirely. Even in the "light" gauge its huge and high tension, with a really unique twisting pattern. It was clear like a gut D and was pretty quick for a huge ol' gut string. I found this string much more usable pizz than the Mari, but it still slapped great. Its also insanely expensive!
You might want to consider the copper-and-silk Velvet Garbo Light E and A as well. Reasonably priced compared to gut, loud acoustically, totally flatwound, very slap friendly.
Last edited by HateyMcAmp : 08-21-2013 at 01:23 PM.